Mercedes Motorsport boss Toto Wolff has sold more of his Williams shares to American entrepreneur Brad Hollinger.

Speaking at a media briefing, Wolff, who sold 5% of his stake in Williams to Hollinger in June 2014, with an option on a further 2%, said his latest sale had left him with just short of a five percent holding in the Grove outfit.

"I have no plans to change it," he added, according to Reuters.

Hollinger is not well-known in the world of F1. He made is money through a company he founded called Vibra Healthcare. It owns hospitals across the United States and Hollinger is its chief executive.

Following the original sale, Wolff described Hollinger as a "shrewd business man, a racing fan who owns vintage F1 cars. He bought into Williams as a financial/fun investment. He does not want to get involved but he is bullish about Formula One's long-term business case."

His latest acquisition puts Hollinger on the same footing as team co-founder Patrick Head, who owns 10 percent of the team, while Frank Williams retains 52 percent stake.

Currently, Williams is the only quoted F1 team and Wolff was one of the driving forces behind that flotation. However, in 2013 he was poached by Mercedes, helping it to win both titles just a year later.

At a time many fear for the sport's future, Hollinger is not so despondent, claiming that he feels F1 is "on the cusp of another major explosion".

"I am never in business not to make money," he said, according to Reuters. "I think there is a huge opportunity in Formula One.

"It has not really tapped significantly the whole social media route in terms of streaming information out to the masses on whatever medium you might choose," he added. "Formula One has been incredibly successful despite the fact it has not really taken hold significantly in the US, and I think the opportunity exists. I think the future is really bright in the United States."

Wolff's wife, Susie, remains test driver at Williams, which finished third in the 2014 Constructors' Championship, its amazing revival in fortune aided, in part, by the Mercedes power units in the rear of the FW36s.